Components made of cast material and particularly cast iron as well as sheet metal material are used in exhaust systems. Components made of cast material are particularly used when continuously variable transitions or complicated flow paths shall be formed, whereas components made of sheet metal material are used, when constant cross sections shall be maintained for a certain length. An example of a component made of a cast material is the exhaust elbow, an example of a component made of a sheet metal material is the exhaust pipe. The connection between a component made of a cast material and a component made of a sheet metal material is frequently established by means of soldering or welding. A component made of a cast material which is permanently connected with a component made of a sheet metal material is designated as assembly unit in the present document.
Because of the different thermal expansion properties of the materials made of cast material and of sheet metal material, which can also be attributed to different wall thicknesses, problems, which may lead to a leaking of the assembly unit overall, frequently arise in the connection area between components made of cast material and components made of sheet metal material.